Yasuyuki Ozeki 교수

We theoretically show that the shot-noise-limited sensitivity of stimulated Raman scattering (SRS) microscopy, which enables high-contrast vibrational imaging, is similar to that of coherent anti-Stokes Raman scattering microscopy. We experimentally confirm that the sensitivity of our SRS microscope is lower than the shot-noise limit only by <15 dB, which indicates that the high-sensitivity of SRS microscopy is readily available.

By virtue of the combined merits of flow cytometry and fluorescence microscopy, imaging flow cytometry (IFC) has become an established tool for cell analysis in diverse biomedical fields such as cancer biology, microbiology, immunology, hematology, and stem cell biology. However, the performance and utility of IFC are severely limited by the fundamental trade-off between throughput, sensitivity, and spatial resolution. Here we present an optomechanical imaging method that overcomes the trade-off

We propose and demonstrate the use of subharmonically synchronized laser pulses for low-noise lock-in detection in stimulated Raman scattering (SRS) microscopy. In the experiment, Yb-fiber laser pulses at a repetition rate of 38 MHz are successfully synchronized to Ti:sapphire laser pulses at a repetition rate of 76 MHz with a jitter of <8 fs by a two-photon detector and an intra-cavity electro-optic modulator. By using these pulses, high-frequency lock-in detection of SRS signal is accomplished

Imaging of biological cells and tissues with subcellular spatial resolution is important in biology and medicine because it allows us to explore the dynamics of cells and to diagnose the structure of tissues. Among various optical imaging modalities, laser microscopy with fluorescent staining is a powerful method for this purpose. However, it still suffers from the limited applicability and cytotoxicity of a staining process. Stimulated Raman scattering (SRS) microscopy is an emerging technique

We demonstrate direct microwelding between glass and copper substrates by use of femtosecond (fs) pulses. The joint strength is as high as >16 MPa. A scanning electron microscopy cross-sectional image of the sample proves successful joining without voids or cracks. Furthermore, we show that, compared with ns-pulses, the use of fs-pulses can reduce the pulse energy required for welding by two orders of magnitude, leading to the suppressed effect of heat and to the precise control of the welded re

We demonstrate a technique of hyperspectral imaging in stimulated Raman scattering (SRS) microscopy using a tunable optical filter, whose transmission wavelength can be varied quickly by a galvanometer mirror. Experimentally, broadband Yb fiber laser pulses are synchronized with picosecond Ti:sapphire pulses, and then spectrally filtered out by the filter. After amplification by fiber amplifiers, we obtain narrowband pulses with a spectral width of <3.3 cm(-1) and a wavelength tunability of >225

By using the concept of a stationary rescaled pulse (SRP), we analyze an adiabatic soliton compression system based on dispersion-decreasing fiber (DDF). We show that a SRP can exist in a DDF with a linearly decreasing dispersion profile and that the SRP resembles a linearly chirped sech2 pulse. According to the analysis, we show numerically that pedestal-free pulse compression is possible by using the SRP.

A 10 GHz similariton pulse train is generated from a 1.2 km-long erbium-doped fibre amplifier and applied to a multi-wavelength pulse source. Slicing the spectrum of the similariton pulse train, a 10 Gbit/s transmitter was constructed, which has excellent Q-factors of over 25.3 dB in the entire bandwidth. Such uniform characteristics of the sliced pulse train originate from the high spectral flatness of the similariton.

Experimentally generated is a 1 THz, 97 fs optical pulse train at 1.55 cm wavelength region based on a comb-like profiled fibre, which consists of 15 pairs of highly nonlinear fibres (HNLFs) and standard singlemode fibres. Such high-repetition rate pulse generation in the 100 fs regime was made possible by the HNLF with high nonlinearity and small dispersion slope.

We experimentally investigate fast wavelength-tuning characteristics of a polarization-maintaining Er fiber laser, which is mode-locked with a semiconductor saturable absorber mirror. Wavelength tuning was accomplished with an intracavity filter incorporating a galvanometer mirror and a diffraction grating. Within the tunability of 30 nm, we achieved a wavelength-tuning speed of <5 ms. We also show that the variation of repetition rates can be suppressed to <200 Hz by simply shifting the positio